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This paper concentrates on equilibrium behavior of fluids in low or zero gravity, and sloshing in normal and low gravity. Included are a background and review of the literature, and an introduction to a new equivalent mechanical model.
The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B Spacecraft liquid helium container tank without probe imposed by various frequencies of gravity jitter have been investigated. Results disclose the conditions for the excitation of large amplitude slosh waves which should be avoided in the design of cryogenic liquid propellant system.
Preliminary attitude and articulation controller designs for the CRAF/Cassini spacecraft have prompted a consideration of potential interactions with structural dynamics and propellant motion. The two algorithms significantly affected are attitude control during main engine burns, and articulation control of the high-precision scan platform (HPSP). For main engine burns, the primary concerns are the sloshing of the bipropellant, which constitutes 70 percent of initial spacecraft mass, and the vibration of the three large appendages, especially the HPSP, on which the gyros are mounted. For the HPSP pointing algorithm, the main concern is the fairly large offset of the HPSP center-of-mass from the gimbals, which is motivated by other system and subsystem considerations. This offset results in significant coupling between HPSP articulation and HPSP boom structural dynamics. This paper surveys the operational scenarios of these algorithms, and the impacts of nonrigid dynamics on controller design and performance.
This paper describes the status and plans for the work being performed under NASA NRA contract NASW-4803 so that members of the Microgravity Fluid Dynamics Discipline Working Group are aware of this program. The contract is a cross-disciplinary research program and is administered under the Low Temperature Microgravity Research Program at the Jet Propulsion Laboratory. The purpose of the project is to perform low-gravity verification experiments on the slosh behavior of He II to use in the development of a CFD model that incorporates the two-fluid physics of He II. The two-fluid code predicts a different fluid motion response in low-gravity environment from that predicted by a single-fluid model, while the 1g response is identical for the both types of model.
Measured two-dimensional damping forces of baffles with various shapes and perforations are presented for fluid conditions representative of those in liquid-fuel rocket vehicles. The effect of amplitude and frequency of fuel sloshing, and surface proximity on baffle damping are shown. Application of the result sin the prediction of damping effectiveness of ring baffles in cylindrical tanks is demonstrated. Finally, some measurements of damping in a free-free cylindrical tank are presented which verify the predictions based on two-dimensional results. Measurements of certain three-dimensional baffles show that they provide greater damping than ring baffles.
Coupling computational fluid dynamics (CFD) with a controls analysis tool elegantly allows for high accuracy predictions of the interaction between sloshing liquid propellants and the control system of a launch vehicle. Instead of relying on mechanical analogs which are n0t va lid during all stages of flight, this method allows for a direct link between the vehicle dynamic environments calculated by the solver in the controls analysis tool to the fluid now equations solved by the CFD code. This paper describes such a coupling methodology, presents the results of a series of test cases, and compares said results against equivalent results from extensively validated tools. The coupling methodology, described herein, has proven to be highly accurate in a variety of different cases.
Coupling computational fluid dynamics (CFD) with a controls analysis tool elegantly allows for high accuracy predictions of the interaction between sloshing liquid propellants and th e control system of a launch vehicle. Instead of relying on mechanical analogs which are not valid during aU stages of flight, this method allows for a direct link between the vehicle dynamic environments calculated by the solver in the controls analysis tool to the fluid flow equations solved by the CFD code. This paper describes such a coupling methodology, presents the results of a series of test cases, and compares said results against equivalent results from extensively validated tools. The coupling methodology, described herein, has proven to be highly accurate in a variety of different cases.
A scalable computational approach to the simulation of propellant tank sloshing dynamics in microgravity is presented. In this work, we use the lattice Boltzmann equation (LBE) to approximate the behavior of two-phase, single-component isothermal flows at very low Bond numbers. Through the use of a non-ideal gas equation of state and a modified multiple relaxation time (MRT) collision operator, the proposed method can simulate thermodynamically consistent phase transitions at temperatures and density ratios consistent with typical spacecraft cryogenic propellants, for example, liquid oxygen. Determination of the tank forces and moments is based upon a novel approach that relies on the global momentum conservation of the closed fluid domain, and a parametric wall wetting model allows tuning of the free surface contact angle. Development of the interface is implicit and no interface tracking approach is required. A numerical example illustrates the method's application to prediction of bulk fluid behavior during a spacecraft ullage settling maneuver.
This paper compares a fluid/thermal simulation, in Fluent, with a low-g, nitrogen slosh and boiling experiment. In 2010, the French Space Agency, CNES, performed cryogenic nitrogen experiments in a low-g aircraft campaign. From one parabolic flight, a low-g interval was simulated that focuses on low-g motion of nitrogen liquid and vapor with significant condensation, evaporation, and boiling. The computational results are compared with high-speed video, pressure data, heat transfer, and temperature data from sensors on the axis of the cylindrically shaped tank. These experimental and computational results compare favorably. The initial temperature stratification is in good agreement, and the two-phase fluid motion is qualitatively captured. Temperature data is matched except that the temperature sensors are unable to capture fast temperature transients when the sensors move from wet to dry (liquid to vapor) operation. Pressure evolution is approximately captured, but condensation and evaporation rate modeling and prediction need further theoretical analysis.
The proposed paper will compare a fluid/thermal simulation, in FLUENT, with a low-g, nitrogen slosh experiment. The French Space Agency, CNES, performed cryogenic nitrogen experiments in several zero gravity aircraft campaigns. The computational results have been compared with high-speed photographic data, pressure data, and temperature data from sensors on the axis of the cylindrically shaped tank. The comparison between these experimental and computational results is generally favorable: the initial temperature stratification is in good agreement, and the two-phase fluid motion is qualitatively captured.
In recent years, considerable effort has been devoted to studying the future use of liquid methane (LCH4) in land, air, and space vehicle applications because of its high density and handling characteristics. This work presents a validation of computational tools for the thermodynamics characterization of a propellant tank undergoing sloshing and draining-induced thermal destratification as part of our continuous effort to improve simulation capabilities for support of NASA’s current and future flight programs. A multi-phase computational fluid dynamics (CFD) code developed at NASA MSFC, Loci/STREAM-VOF, is applied to predict gaseous pressurant requirements during the ramping, holding, and draining phases of operation with liquid methane. The experimental work conducted at the NASA K-site facility is used for validation. The effort showed that Loci/STREAM-VOF is capable of capturing the important findings from the previous experiments: (1) the pressurant mass required increases with the expulsion time due to longer mass transfer time at the interface; and (2) the pressurant mass required decreases with the increase in inlet temperature. Comparison with experimental data shows consistent good agreement at different expulsion times and different inlet gas temperatures.
In recent years, considerable effort has been devoted to studying the future use of liquid methane (LCH4) in land, air, and space vehicle applications because of its high density and handling characteristics. This work presents a validation of computational tools for the thermodynamics characterization of a propellant tank undergoing sloshing and draining-induced thermal destratification as part of our continuous effort to improve simulation capabilities for support of NASA’s current and future flight programs. A multi-phase computational fluid dynamics (CFD) code developed at NASA MSFC, Loci/STREAM-VOF, is applied to predict gaseous pressurant requirements during the ramping, holding, and draining phases of operation with liquid methane. The experimental work conducted at the NASA K-site facility is used for validation. The effort showed that Loci/STREAM-VOF is capable of capturing the important findings from the previous experiments: (1) the pressurant mass required increases with the expulsion time due to longer mass transfer time at the interface; and (2) the pressurant mass required decreases with the increase in inlet temperature. Comparison with experimental data shows consistent good agreement at different expulsion times and different inlet gas temperatures.
Dynamic analysis of liquid in a spherical tank with applications to trajectory failure and loss of control in missile and rocket flight
Forces and moments of liquid propellant oscillation in cylindrical tanks caused by structural bending
Natural frequencies and modes of oscillation of liquids in partially filled axisymmetric ellipsoidal tanks calculated, using variational principle
Damping of liquid oscillations in cylindrical tanks, determining rigid and flexible baffle loss coefficients, baffle efficiency and maximum bending stress
Design of baffles to damp liquid propellants in rocket vehicles
Coupled oscillations of elastic container partially filled with incompressible liquid